Gas-fired kiln



A. G. BOYLES GAS-FIRED KILN March 6, 1962 2 Sheets-Sheet 1 Filed Jan.15, 1960 INVENTOR. Ala/v20 6. 50 255 BY Airmen/5 y A. G. BOYLES GASJIREDKILN March 6, 1962 2 Sheets-Sheet 2 Filed Jan. 15, 1960 INVENTOR.Aid/V20 G. 50 15 ArraZNz-IY United States Patent Q 3,023,478 GAS-FIREDKILN Alonzo G. Boyles, Box 34, New Cumberland, W. Va. Filed Jan. 15,1960, Ser. No. 2,726 3 Claims. (Cl. 25-145) This invention relates tokiln and oven constructions, and more particularly to gas-fired kilns ofthe downdraft type for calcining bricks, clay pipe or other clayproducts.

While the firing of kilns and ovens by various types of fuel, such aswood, coal, oil and gas, is common practice in the treatment of clayproducts, the results have not been altogether successful because of thedifiiculty in obtaining the proper circulation of the combustion gasesin order to insure the complete and uniform heating of the products. Insome instances the kilns are constructed so as to provide a series ofupright, circumferentially-spaced, fuel boxes built into the side Wallof the kiln chamber with the tops of the fuel boxes opening below andadjacent the roof of the chamber, causing the combustion gases to bedirected vertically-upward against the roof near its outer edge. Suchkilns, as exemplified by the patent of Walter B. Wright, Ser. No.405,935, are subject to the objection that the concentrated streams ofhot gases impinging against the roof produce hot spots that tend torapidly burn out the lining, both along the side wall of the kiln aswell as at localized areas of the roof. Furthermore, much of the heat ofthe gases is dissipated by reason of being absorbed by the kilnstructure rather than usefully employed in heating the clay products.

In other types of kilns, as typified by the patent of John T. Underwoodet al., No. 1,224,978, the hot combustion gases are directed centrallydownwardly through the roof directly upon the clay products, so that theclay products stacked immediately below the inlet for the combustiongases are exposed to the full blast of the gases, which are reflectedback against the roof, causing either overheating or underheating of theclay products, depending upon their position in line or out of line withthe gas stream. In either case, the location of the combustion zone issuch that the flow of the hot gases throughout the kiln is not conduciveto the best performance of the kiln, even though means are provided, assuggested by the patents referred to above, intended to overcome theobjections.

It is an important object of the present invention to provide agas-fired kiln or oven of the down-draft type in which the hotcombustion gases delivered by the gassupply nozzles flood the top of thekiln chamber producing a zone of maximum temperature in the area belowthe roof of the kiln and above the stack of clay products to be calcinedand without direct impingement upon either a portion of the kilnstructure or upon the clay products being treated. Consequently, thereis induced a substantially even and unobstructed flow of the gasesdownwardly over and through the stack which completely bathes the clayproducts in an atmosphere of hot gases and causes an even and thoroughpenetration of heat into such products.

Another object of the invention is to provide a gasfired kiln or oven ofthe above character in which there is provided a plurality of laterallyspaced burner units arranged in the wall of the kiln adjacent its rooffor discharging hot combustion products inwardly of the kiln and towardsits roof in a manner such as to promote the downward passage of the hotcombustion products through the stack of clay productsbeing fired.

Yet another feature of the invention is to provide a gas-fired kiln ofthe above character in which the wall of each of the burner unitsincludes a plurality of reice movable, inter-fitting slabs, whereby theburner units may be easily relined as this becomes necessary from timeto time.

Still another object of the invention is to provide a gas-fired kiln oroven of the above character which is of comparatively simple andinexpensive construction, which is efiicient and cheap in operation, andwhich may be expeditiously built and installed, either as originalequipment or by converting currently used types of kilns into kilnsembodying the novel features of the invention.

The foregoing and other objects, advantages, and fea tures of theconstruction will become apparent from a consideration of the followingdetailed description of a preferred embodiment of the inventionconsidered in connection with the accompanying drawings, in which:

FIGURE 1 is a plan view of a kiln embodying the novel structure of thepresent invention;

FIGURE 2 is a vertical sectional view on an enlarged scale, of the kilntaken substantially upon a plane passing along section line 2-2 ofFIGURE 1, illustrating the structural arrangement of one of the burnerunits in relation to the kiln;

FIGURE 3 is a transverse, plan sectional view taken substantially upon aplane passing along section line 3-3 of FIGURE 2, illustrating furtherstructural details of a burner unit and its relationship to the kiln;

FIGURE 4 is a detailed sectional view taken substantially upon a planepassing along section line 44 of FIGURE 3, and illustrating, on anenlarged scale, the structural arrangement of the removable slabs of aburner unit,

FIGURE 5 is a side view of a portion of a kiln similar to that of FIGURE6 but including certain modifications;

FIGURE 6 is a detailed view of the kiln taken on the line 6-6 of FIGURE5; and

FIGURE 7 is a detailed top sectional view of the fan housing taken onthe lines 7-7 of FIGURE 6.

For purposes of illustration, the present invention has been illustratedin connection with a cylindrical type of kiln having a dome-shaped roof.The kiln comprises a circumferential wall 10 closed at its top by acrown 12, both the wall and crown being made of brick in theconventional manner and lined by some refractory material 10a towithstand and prevent loss of heat from the closed chamber. The bottomof the chamber is provided with a floor or hearth 14 formed of brickarranged in checker formation so as to define outlet openings 16extending through the hearth. These outlets communicate with subflues orpassageways 18 below the hearth which, in turn, lead to a chimney (notshown) outside the kiln. As shown in FIGURE 2, the clay products 20 (asindicated in broken lines) to be calcined are stacked or otherwisearranged in spaced and staggered relation on the hearth to permit thedownward passage of hot combustion gases over, through, around andbetween the clay products for their complete exposure to the hot gases.

Mounted on the top of the crown 12 exteriorly of the chamber is anannular gas supply pipe or manifold 22 connected to a source ofcombustible gas by suitable pipe line 24. At circumferentially spacedpoints around the supply pipe 22 there are connected down-pipes 26. Theannular pipe 22 does not extend completely around the top 12 of the kilnbut has its ends spaced apart a distance equal to the circumferentialspacing between adjacent down-pipes 26. v

As illustratedin FIGURES 2 and 3, each of the downpipes 26'terminates inan inwardly directed and upwardly inclined burner nozzle 28 which isdisposed within a 'burner orifice 30. The burner orifice extends throughthe wall 10 of the kiln and communicates with the heating chamberadjacent to but below the inner surface of the crown 12. As bestillustrated in FIGURE 2, the longitudinal axis of the orifice 30 isinclined upwardly and inwardly towards the crown 12 so that the hotcombustion gases discharged from the orifice will initially be directedradially inward and at an upward inclination to produce a zone ofmaximum heat within the area below the crown and above the stack of clayproducts.

The burner apertures 30 pass completely through the wall of the kiln andeach aperture is lined with slabs defining a top wall 32, a bottom wall34 and side walls 36 all of which diverge from the outer end of theorifice located on the outer circumference of the kiln toward the innerend of the orifice located on the inner circumference of the kiln. Theslabs constituting the two side walls 36 have longitudinal tongues orprojections 38 thereon for reception in corresponding grooves 38a on thefacing surfaces of the slabs forming the bottom wall 34 and the top wall32. Thus, by removing the trapezoidalshaped slabs 32, 34 and 36, thelining for an entire burner orifice may be removed by simply knockingthe slabs inwardly into the interior of the chamber. Thetongue-andgroove interfit of the slabs facilitates the wedging assemblyof the slabs in the burner orifices and subsequently maintains themagainst buckling during the operation of the kiln.

Surrounding each nozzle 28 is a space which forms an air flow passage.Such air flow may be induced by the combustion taking place in thechamber or when the kiln is to be operated under forced draft acentrifugal fan 40, powered by an electric motor 42, may be provided.The fan 40 may be of any suitable type, such as a squirrel cage fan orthe like, and there may be a single fan for each burner unit; or,alternatively, there may be an air manifold with a single fan connectedthereto for pressurizing the air. The air passing between the burnernozzle and the slabs lining the burner orifice tends to reduce thetemperature upon the slabs and also serves to propel the hot combustiongases or flame into a zone located centrally of the chamber and belowthe top of the kiln. Thus, the hot combustion gases will pass downwardlyover, through, around and between stacks of clay products sup ported onthe hearth.

From the foregoing description, it will be apparent that the gasesdelivered by the burner nozzles 28 located in circumferentially spacedrelation around the wall of the kiln will expand in their passagethrough the orifices 30 and be directed by such orifice upwardly andinwardly of the kiln chamber, filling the upper end of the chamber withflame and hot combustion gases and while avoiding direct impingement ofthe gases issuing from the orifices either upon any part of the kilnstructure or upon the stacked supply of clay products. The hotcombustion gases in their passage through the chamber to the outlets 16in the hearth of the chamber will circulate over and through the stack,subjecting the exposed surfaces of the clay products to. a thorough anduniform heating. Because only a minimum amount of heat is absorbed bythe kiln structure, the major portion of the heat of the gases isusefully employed in heating the clay products with a resultant economyof fuel consumption and a reduction of the time required for kilnoperation.

Moreover, the slabs 32, 34 and 36 lining the burner orifices 30 may bequickly renewed when necessary by simply knocking out the burnt-outslabs and replacing them with new ones. The tongue-and-groove interfitbetween the slabs insures the proper initial erection of the slabswithin the orifices as well as maintains the slabs against bucklingunder the high temperature of the kiln. If desired, the cracks betweenthe slabs and the sides of the orifices may be sealed with a refractorycement.

The gas-fired burner assembly may be employed with various diiferenttypes of kilns which may be either round, rectangular or the like, withthe size. of the gas burner nozzle being variable depending upon thecapacity of the kiln. The details of the kiln per se have not beendescribed since various kiln constructions are 4 well known in the artand form no essential part of the present invention. This invention alsois readily adaptable for converting present known types of kilns to thegas-fired type employing the burner assemblies in the manner describedabove.

As was stated above, there may be a single fan for each burner unit (orfor certain of the several burner units) or there may be an air manifoldrequiring but a single fan for pressurizing the air. This lattermodification is illustrated in FIGS. 5, 6 and 7 of the drawing in whichthe kiln corresponds in all other major respects to the kiln of FIGS. 1through 4.

The air supply manifold according to this modification comprises a duct50 skirting the circumferential edge of the crown 12 in generallyconcentric relation to the gas supply manifold 22. The duct 50 does notdefine a closed circle but instead its circle is interrupted to providespace for a housing or plenum chamber 51 with which the ductcommunicates through openings in the two opposite side walls of thehousing. A fan 52 is located within the housing 51 and is driven by anelectric motor 53 to draw air into the housing through an inlet 54, andto forcibly discharge it against a V-shaped deflector plate 54 whichdirects the air into the two ends of the communicating duct 50. The duct50 is thus supplied with air under pressure during operation of thekiln.

At radially spaced locations around the kiln, corresponding to thelocations of the burner orifices 30, drop pipe 55, communicating at oneend with the air manitold 50, extend vertically downwardly upon theoutside of the wall 10 of the kiln and terminate adjacent the burnerorifices 30. Each dropv pipe 55 is divided at its lower end into twobranches 55a and 55b which are directed inwardly of the kiln and passthrough openings in an air box 56 closing the outer end of a burnerorifice. Thus, air delivered by a drop pipe from the air manifold 50 isdischarged into the air box and thence into the burner orifice in twostreams of equal volume upon opposite sides of a burner nozzle 28. Forcontrolling the volume of air fed to each burner unit, there is provideda damper 57 which can be manually regulated to produce the desiredheating conditions within the kiln.

In the manufacture of glazed earthenware it is customary to introduce asilica composition into the kiln atmosphere which will condense and forma film upon the surface of the products being treated. For this purposea hopper 58 may be mounted exteriorly upon the kiln wall in the vicinityof, and preferably at an elevation above, each burner aperture forcontaining a supply of glaze composition. Each hopper 58 discharges atits bottom through a spout 59 that terminates within a burner aperture30. The fast moving air and gases passing through the burner aperturecatch up and sweep the glaze composition into the kiln. A valve (notshown) may be provided for controlling the feed of glaze to the burnerorifice. Such hoppers may also be used in the embodiment; of theinvention described in connection with FIGS. 1 through 4, since thisfeature is not dependent upon any special manner in which air issupplied to the kiln. Also it will be apparent that the air manifold maybe arranged with respect to the kiln in other ways than that describedabove. For example, the air manifold may rest or be supported upon thecrown 12 inwardly of the circumferential edge of the kiln adjacent toand concentric with the gas manifold 22. Nor is it essential that all ofthe burner units be supplied with air under pressure but certain of theburner orifices, or all of them, may receive their supply of air bynatural draft through unobstructed burner orifices. By providing asingle fan for servicing all the burner units, instead of an individualfan for each burner unit, economy in the construction and operation ofthe kiln is achieved.

While this invention has been described in a specific form and asoperating in a specific manner for the purpose of illustration, it is tobe understood that the inven- 5 tion is not limited thereto, sincevarious modifications will suggest themselves to those skilled in theart without departing from the spirit of this invention, the scope ofwhich is set forth in the annexed claims.

I claim:

1. A gas-fired kiln for heat treating stacks of bricks and other clayproducts, comprising a substantially closed chamber having a continuouscircumferential vertical side wall, a crowned roof having an arcu-ateinterior surface shaped to produce a uniform downdraft of hot gasesflowing into the interior of the chamber, a plurality of gas entranceports located at equally spaced intervals laterally around thecircumference of the chamber in the vertical side Wall at an elevationjust below the crowned roof, each of said ports extending entirelythrough the side Wall in the form of a truncated pyramid so as toincrease uniformly in cross-sectional area inwardly of the kiln andbeing inclined angularlly upwardly to direct the inflowing hot gasestoward a zone just below the arcu-ate interior surface of the roofcentrally thereof without impinging directly onto said surface, saidports having an easily removable and replaceable refractory liningcomposed of interengaging flat trapezoidal slabs mounted on each of thesides thereof, an injection nozzle for combustible gas positionedsubstantially centrally of each of said ports, and means for blowing airinwardly through the ports around the nozzles to support combustion ofthe gas therein.

2. The gas-fired kiln defined by claim 1, wherein the combustible gas issupplied to all of the nozzles simultaneously at a uniform flow ratethrough a manifold extending around the side Wall of the kiln, and themeans for blowing air inwardly through the ports is an individual fanmounted on the exterior of each port.

3. The gas-fired kiln defined by claim 1, wherein a first manifoldextending around the side Wall of the kiln supplies the combustible gasto all of the nozzles simultaneously at a uniform rate, and a secondmanifold extending around the kiln and having a fan therein constitutesthe said means for blowing air inwardly through the ports around thenozzles.

References Cited in the file of this patent UNITED STATES PATENTS510,819 Reppell Dec. 12, 1893 1,128,146 Jacobs Feb. 9, 1915 1,231,224Warner June 26, 1917 1,411,534 Straight Apr. 4, 1922 1,615,217 DresslerJan. 25, 1927 1,646,254 Meehan Oct. 18, 1927 1,894,249 Williams Jan. 10,1933 1,919,322 Dressler July 25, 1933 2,192,682 Anderson Mar. 5, 19402,192,752 Miller Mar. 5, 1940 2,403,431 Dobn'n July 9, 1946 2,805,709Dailey Sept. 10, 1957

